1. Field of the Invention
The present invention relates to opening and closing devices used in electronic devices such as mobile phones and personal computers.
2. Background Art
With electronic devices such as mobile phones and personal computers becoming increasingly smaller and lighter, many products are adopting designs that attach a movable housing to a fixed housing in an openable and closable fashion, a so-called folding design. The opening and closing devices used in these electronic devices are also required to ensure further reliable opening and closing operations.
A conventional opening and closing device is described next with reference to FIGS. 8 to 10.
FIG. 9, a sectional view, is magnified radially for easier understanding of the relation between a stator cam and rotor cam. The central axis is indicated as X1-X2 for description.
FIG. 9 is a sectional view and FIG. 10 is an exploded perspective view of the conventional opening and closing device. Opening and closing device 10 has roughly cylindrical stator 1 and roughly cylindrical rotor 3.
Stator 1 includes fixed part 1A formed at its left end face, and a pair of opposed stator cams 2 on its outer periphery at the right end. Each of stator cams 2 includes protrusion 2A and tilting portions 2B and 2C extending from protrusion 2A.
Rotor 3 is disposed in a rotatable fashion in opening and closing directions and also in a movable fashion along center axis X1-X2 relative to stator 1. Rotor 3 includes a pair of rotor cams 4 opposed to each other relative to central axis X1-X2 on its outer periphery at the left end, which is a face opposed to stator 1.
Opening and closing device 10 also has roughly cylindrical case 5 and coil spring 6. Stator 1 and rotor 3 are housed in case 5. Spring 6 is set between a right end face of rotor 3 and an inner side face of case 5 in a little contracted state. This spring 6 applies a force toward X1 to rotor 3, and thus tips of rotor cams 4 resiliently contact tilting portions 2B of stator cams 2.
Opening and closing device 10 also has roughly columnar fixed shaft 7.
Stator 1 is secured to the left end of this fixed shaft 7. Fixed part 1A rotatably protrudes from a left end face of case 5. The right end of fixed shaft 7 passes through a hollow portion of rotor 3 and spring 6, and is secured to cover 8. Cover 8 is rotatably attached to case 5, and thus fixed shaft 7 is also rotatable relative to case 5.
An example of employing opening and closing device 10 in a mobile phone is described next.
FIG. 8B is a perspective view of the mobile phone employing opening and closing device 10. Fixing part 1A of stator 1 is secured to fixed housing 22 where control panel 22A such as keys and sound input part 22B such as a microphone are formed on its top face. Case 5 is attached to movable housing 23 where display 23A such as LCD and sound output part 23B such as a speaker are formed on its surface. With this opening and closing device 10, movable housing 23 is journaled relative to fixed housing 22 in an openable and closable fashion in the mobile phone shown in FIG. 8B.
When movable housing 23 is closed relative to fixed housing 22, as shown in FIG. 8A, opening and closing device 10 is in the state shown in FIG. 9. More specifically, tips of rotor cams 4, to which spring 6 applies a force, resiliently contact lower tilting portions 2B of stator cams 2. Spring 6 applies a force toward X1 in a closing direction, which is downward in FIG. 9, to rotor 3. Consequently, a force in the closing direction is applied to movable housing 23 where case 5 is attached, and thus movable housing 23 is retained in a closed state.
When the movable housing 23 is opened by hand from this closed state, case 5 secured to movable housing 23 rotates, and rotor 3 rotates as it moves toward direction X2 inside case 5. As rotor 3 rotates, the tips of rotor cams 4 ride over projecting portions 2A of stator cams 2, and resiliently contact upper tilting portions 2C. At tilting portions 2C, spring 6 applies a force toward direction X1 in an opening direction to rotor 3. This spring force applies a force in the opening direction to movable housing 22. Accordingly, as show in FIG. 8C, movable housing 23 is opened at a predetermined angle relative to fixed housing 22. Here, the opening direction is equivalent to a counterclockwise rotation when the closing direction is a clockwise rotation relative to central axis X1-X2 seen from the X1 side. Contrary, the closing direction may be a counterclockwise rotation.
A separate stopper mechanism (not illustrated) may be provided between movable housing 23 and fixed housing 22 to retain movable housing 23 at an angle, for example 165°, which is convenient for conversation using sound input part 22B and sound output part 23B
In other words, when case 5 attached to movable housing 23 is rotated while the tips of rotor cams 4 are resiliently contacting tilting portions 2B or 2C of stator cams 2, rotor 3 moves in the direction of central axis X1-X2, and rides over projecting portion 2A. When rotor 3 rides over projecting portion 2A, the tips of rotor cams 4 resiliently contact either tilting portions 2B or 2C, which are different from the initial state.
As described above, a pair of opposed rotor cams 4 are disposed on the outer periphery at the left end of rotor 3. These rotor cams resiliently contact and slide on the pair of stator cams 2 which are also opposed to each other. These tips of rotor cams 4 have a predetermined width in a circumferential direction although they are thinned widthwise in the circumferential direction compared to that of the base part. Accordingly, an angle that movable housing 23 opens relative to fixed housing 22 becomes smaller for the angle equivalent to the width of rotor cams 4.
More specifically, with conventional opening and closing device 10, movable housing 23 is impossible to open 180° relative to fixed housing 22. Practically, a width in the circumferential direction equivalent to about several tens of degrees is needed for rotor cams 4. Accordingly, a force toward the opening direction is not applied to case 5 attached to movable housing 23 when movable housing 23 is opened about 150°. The conventional opening and closing device is typically disclosed in Japanese Patent Unexamined Publication No. 2004-245342.
In the above conventional opening and closing device, no force toward the opening direction is applied when movable housing 23 is opened not less than 165° for a phone call. Accordingly, it is difficult to retain movable housing 23 at a predetermined angle relative to fixed housing 22. This often causes wobbling of movable housing 23 in the opening and closing direction.